1. Field of the Invention
The present invention relates to an apparatus for inspecting a wafer. More particularly, the present invention relates to an apparatus for inspecting defects of a wafer using images acquired by a charge coupled device (CCD) camera.
2. Description of the Related Art
Generally, semiconductor devices are manufactured through a three-step process. First, a fabricating process is performed to form an electrical device, such as a transistor and a capacitor, on a silicon wafer used as a semiconductor substrate. Second, an inspecting process is performed to inspect electrical characteristics of the semiconductor devices formed on the semiconductor substrate. Third, a packaging process is performed to package the semiconductor devices to protect the semiconductor devices and to enable the installation of the semiconductor devices in the various information communication devices.
The fabricating process typically includes a film deposition process for forming a specific film on the wafer, a chemical and mechanical polishing (CMP) process for planarizing a surface of the film, a photolithography process for forming photoresist patterns on the film, an etching process for forming the film into patterns having the electrical characteristics using the photoresist patterns, an ion implantation process for implanting specific ions into specific portions of the film, a cleaning process for removing impurities remaining on the wafer, an inspection process for inspecting defects of the film and patterns formed on the wafer, or other similar processes.
Recently, causes of defects have become more varied as diameters of wafers have increased and a degree of integration of the semiconductor device has increased. Accordingly, the inspection process has become more important to determine the causes of the defects and to cope effectively with the defects.
An optical microscope or an electron microscope may be employed for the inspection process. Examples of an optical microscope include a charge coupled device (CCD) camera having a light source for illuminating a surface of the wafer, a lens with a high magnifying power, and a CCD memory for converting an image magnified by the lens into image data and for memorizing the image data. Examples of an electron microscope include a scanning electron microscope, a transmission electron microscope, and the like.
The inspection process is generally performed using an optical microscope because an inspection process using an electron microscope requires a relatively long inspection time and is difficult to inspect side and back surfaces of the wafer. A conventional inspection apparatus using an optical microscope inspects only a front surface of the wafer and is not able to inspect the side and back surfaces of the wafer. Therefore, a conventional inspection process on the wafer requires a plurality of inspection apparatuses thereby increasing the cost related to equipment investment and repair work and deteriorating the productivity of the semiconductor device.
Various attempts have been made to solve the foregoing problems. For example, an apparatus for inspecting all surfaces of the wafer has been developed. In operation, the developed apparatus tilts the wafer to inspect the side and back surface of the wafer. However, the developed apparatus is not able to cope effectively with increasing larger wafer diameters, because it is difficult to stably tilt a wafer having a diameter of 300 mm.